.w{
  width: 1200px;
  margin: 0 auto;
}

#app{
  min-height: 100vh;
}

.nav{
  position: fixed;
  left: 0;
  top: 0;
  width: 100%;
  z-index: 100;
  background-color: #222;
  height: 80px;
  color: #fff;
  transition: .3s linear ;
}

.nav.ceiling{
  color: #222;
  background-color: #fff;
}

.nav_info{
  display: flex;
  justify-content: space-between;
  height: 100%;
  align-items: center;
}
.nav_left{
  font-size: 24px;
  font-weight: 700;
  cursor: pointer;
}

.nav_item{
  font-size: 16px;
  margin-right: 10px;
  cursor: pointer;
}

.nav_left:hover,.nav_item:hover{
  color: skyblue;
}

.banner{
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  background: url(https://images.pexels.com/photos/450035/pexels-photo-450035.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=750&w=1260) no-repeat bottom center/cover;
  height: 100vh;
  margin-top: 80px;
  color: #fff;
}

.banner_title{
  font-size: 32px;
  font-weight: 700;
  margin-bottom: 10px;
  transition: .25s ease-out;
}
.banner_subtitle{
  font-size: 26px;
  transition: .25s ease-out;
}
.banner_title:hover,.banner_subtitle:hover{
  color: skyblue;
  transform: scale(1.1);
}


.article{
  margin-top: 30px;
}
.article_item{
  margin-bottom: 20px;
}

.article_title{
  font-weight: 700;
  font-size: 28px;
  color: #222;
  cursor: pointer;
}

.article_title:hover{
  color: skyblue;
}

.article_content{
  font-size: 16px;
  color: #666;
  line-height: 30px;
}